In addition, a high-energy bidirectional neutron source based on a formula by Ranft showed even further improvement of the fluence results over previous results near the front of the water target where diffusion out the front surface is important. Effects of improved interaction cross sections are modest compared with the addition of the high-energy bidirectional source terms.

A low-energy neutron transport algorithm for use in space radiation protection is developed. The algorithm is based upon a multigroup analysis of the straight-ahead Boltzmann equation by using a mean value theorem for integrals. This analysis is accomplished by solving a realistic but simplified neutron transport test problem. The test problem is analyzed by using numerical and analytical procedures to obtain an accurate solution within specified error bounds. Results from the test problem are then used for determining mean values associated with rescattering terms that are associated with a multigroup solution of the straight-ahead Boltzmann equation. The algorithm is then coupled to the Langley HZETRN code through the evaporation source term. Evaluation of the neutron fluence generated by the solar particle event of February 23, 1956, for a water and an aluminum-water shield-target configuration is then compared with LAHET and MCNPX Monte Carlo code calculations for the same shield-target configuration. The algorithm developed showed a great improvement in results over the unmodified HZETRN solution. In addition, a two-directional solution of the evaporation source showed even further improvement of the fluence near the front of the water target where diffusion from the front surface is important.Heinbockel, John H. and Clowdsley, Martha S. and Wilson, John W.Langley Research CenterNEUTRONS; ALGORITHMS; RADIATION PROTECTION; MATHEMATICAL MODELS; APPLICATIONS PROGRAMS (COMPUTERS); EXTRATERRESTRIAL RADIATION; BOLTZMANN TRANSPORT EQUATION; FLUENCE; WATER; MONTE CARLO METHOD; ENERGY SPECTRA; SOLAR FLARES...

A neutron transport algorithm including both elastic and nonelastic particle interaction processes for use in space radiation protection for arbitrary shield material is developed. The algorithm is based upon a multiple energy grouping and analysis of the straight-ahead Boltzmann equation by using a mean value theorem for integrals. The algorithm is then coupled to the Langley HZETRN code through a bidirectional neutron evaporation source term. Evaluation of the neutron fluence generated by the solar particle event of February 23, 1956, for an aluminum water shield-target configuration is then compared with MCNPX and LAHET Monte Carlo calculations for the same shield-target configuration. With the Monte Carlo calculation as a benchmark, the algorithm developed in this paper showed a great improvement in results over the unmodified HZETRN solution. In addition, a high-energy bidirectional neutron source based on a formula by Ranft showed even further improvement of the fluence results over previous results near the front of the water target where diffusion out the front surface is important. Effects of improved interaction cross sections are modest compared with the addition of the high-energy bidirectional source terms.Clowdsley, Martha S. and Wilson, John W. and Heinbockel, John H. and Tripathi, R. K. and Singleterry, Robert C., Jr. and Shinn, Judy L.Langley Research CenterNEUTRON SOURCES; ALGORITHMS; PARTICLE INTERACTIONS; SHIELDING; BOLTZMANN TRANSPORT EQUATION; RADIATION PROTECTION; EXTRATERRESTRIAL RADIATION; ELASTIC PROPERTIES; WATER; THEOREMS; TARGETS; SOLAR STORMS; SOLAR FLARES; SOLAR CORPUSCULAR RADIATION; RADIATION TRANSPORT; MONTE CARLO METHOD...

This is an authoritative compilation of information regarding methods and data used in all phases of nuclear engineering. Addressing nuclear engineers and scientists at all levels, this book provides a condensed reference on nuclear engineering since 1958.